Optical multilayer film, and optical component and display device comprising the same

Abstract

The optical multilayer film, which comprises a laminate in which a base layer, a primer layer, and a hard coat layer are sequentially laminated, has enhanced mechanical properties while preventing rainbow stains and a reduction in the visibility by adjusting the in-plane retardation of the base layer and the refractive indices of the respective layers. Thus, the optical component and the display device, which comprise the optical multilayer film, have excellent optical characteristics and can operate normally even in harsh environments.

The invention claimed is: 
     
       1. An optical multilayer film, which comprises a laminate in which a base layer, a primer layer, and a hard coat layer are sequentially laminated,
 wherein the base layer comprises a polyester resin and has a minimum in-plane retardation (Ro min ) of 85 nm or less, a change (|ΔRo|/|Δx|) in the in-plane retardation with respect to a displacement in the transverse direction of less than 550 nm/3 m, and a change (|ΔRth|/|Δx|) in the thickness direction retardation with respect to a displacement in the transverse direction of less than 700 nm/3 m, 
 wherein when the refractive indices of the base layer, the primer layer, and the hard coat layer are n1, n2, and n3, respectively, they satisfy the following Equations (1) to (4):
     n 3< n 2< n 1  (1)
 
   0.10≤ n 1− n 3≤0.15  (2)
 
   0≤ n 1− n 2≤0.10  (3)
 
   0≤ n 2− n 3≤0.10  (4), and
 
 
 wherein ΔRo is the change in the in-plane retardation, Δx is the displacement in the transverse direction, and the transverse direction is the width direction of the optical multilayer film. 
 
     
     
       2. The optical multilayer film of  claim 1 , wherein the change (|ΔRo|/|Δx|) in the in-plane retardation with respect to a displacement in the transverse direction is less than 300 nm/3 m. 
     
     
       3. The optical multilayer film of  claim 1 , wherein the base layer has a maximum thickness direction retardation (Rth max ) of 6,000 nm or more. 
     
     
       4. The optical multilayer film of  claim 1 , wherein the base layer has a refractive index (n1) of 1.61 to 1.69. 
     
     
       5. The optical multilayer film of  claim 4 , wherein the base layer has a refractive index (n1) of 1.63 to 1.68, and
 the primer layer has a refractive index (n2) of 1.53 to 1.63. 
 
     
     
       6. The optical multilayer film of  claim 5 , wherein the hard coat layer has a refractive index (n3) of 1.50 to 1.53. 
     
     
       7. The optical multilayer film of  claim 1 , wherein the base layer has a thickness of 20 μm to 60 μm. 
     
     
       8. The optical multilayer film of  claim 7 , wherein the primer layer has a thickness of 50 nm to 120 nm. 
     
     
       9. The optical multilayer film of  claim 8 , wherein the hard coat layer has a thickness of 1 μm to 5μm. 
     
     
       10. The optical multilayer film of  claim 1 , wherein the base layer has a refractive index (n1) of 1.63 to 1.68 and a thickness of 20 μm to 60 μm, the primer layer has a refractive index (n2) of 1.53 to 1.63 and a thickness of 50 nm to 120 nm, and the hard coat layer has a refractive index (n3) of 1.50 to 1.53 and a thickness of 1μm to 5μm. 
     
     
       11. The optical multilayer film of  claim 1 , the primer layer comprises a thermosetting polyurethane-based resin, and
 the hard coat layer comprises a photocurable acrylate-based resin. 
 
     
     
       12. A process for preparing the optical multilayer film of  claim 1 , which comprises:
 (1) extruding a polyester resin to obtain an unstretched sheet; 
 (2) preheating the unstretched sheet at a temperature of 70° C. to 90° C. and then stretching the sheet at a longitudinal stretch ratio (R1) of 2.0 to 5.0 and a transverse stretch ratio (R2) of 2.0 to 5.0; 
 (3) heat setting the stretched sheet at 150° C. to 250° C. to prepare a base layer; and 
 (4) sequentially laminating a primer layer and a hard coat layer on the base layer. 
 
     
     
       13. The process for preparing an optical multilayer film of  claim 12 , wherein the ratio (R1/R2) of the longitudinal stretch ratio to the transverse stretch ratio in the above step (2) is 0.9 to 1.0. 
     
     
       14. An optical component, which comprises a polarizer; and the optical multilayer film of  claim 1  disposed on at least one side of the polarizer. 
     
     
       15. A display device, which comprises a display panel; and the optical component of  claim 14  disposed on at least one of the upper and lower sides of the display panel.